Merge tag 'gpio-fixes-for-v6.14-rc7' of git://git.kernel.org/pub/scm/linux/kernel/git/brgl/linux

Pull gpio fixes from Bartosz Golaszewski:
 "The first fix is a backport from my v6.15-rc1 queue that turned out to
  be needed in v6.14 as well but as the former diverged from my fixes
  branch I had to adjust the patch a bit.

  The second one fixes a regression observed in user-space where closing
  a file descriptor associated with a GPIO device results in a ~10ms
  delay due to the atomic notifier calling rcu_synchronize() when
  unregistering.

  Summary:

   - don't check the return value of gpio_chip::get_direction() when
     registering a GPIO chip

   - use raw notifier for line state events"

* tag 'gpio-fixes-for-v6.14-rc7' of git://git.kernel.org/pub/scm/linux/kernel/git/brgl/linux:
  gpio: cdev: use raw notifier for line state events
  gpiolib: don't check the retval of get_direction() when registering a chip

Author: torvalds

drivers/gpio/gpiolib-cdev.c

@@ -2729,8 +2729,9 @@ static int gpio_chrdev_open(struct inode *inode, struct file *file)
 	cdev->gdev = gpio_device_get(gdev);
 
 	cdev->lineinfo_changed_nb.notifier_call = lineinfo_changed_notify;
-	ret = atomic_notifier_chain_register(&gdev->line_state_notifier,
-					     &cdev->lineinfo_changed_nb);
+	scoped_guard(write_lock_irqsave, &gdev->line_state_lock)
+		ret = raw_notifier_chain_register(&gdev->line_state_notifier,
+						  &cdev->lineinfo_changed_nb);
 	if (ret)
 		goto out_free_bitmap;
 
@@ -2754,8 +2755,9 @@ static int gpio_chrdev_open(struct inode *inode, struct file *file)
 	blocking_notifier_chain_unregister(&gdev->device_notifier,
 					   &cdev->device_unregistered_nb);
 out_unregister_line_notifier:
-	atomic_notifier_chain_unregister(&gdev->line_state_notifier,
-					 &cdev->lineinfo_changed_nb);
+	scoped_guard(write_lock_irqsave, &gdev->line_state_lock)
+		raw_notifier_chain_unregister(&gdev->line_state_notifier,
+					      &cdev->lineinfo_changed_nb);
 out_free_bitmap:
 	gpio_device_put(gdev);
 	bitmap_free(cdev->watched_lines);
@@ -2779,8 +2781,9 @@ static int gpio_chrdev_release(struct inode *inode, struct file *file)
 
 	blocking_notifier_chain_unregister(&gdev->device_notifier,
 					   &cdev->device_unregistered_nb);
-	atomic_notifier_chain_unregister(&gdev->line_state_notifier,
-					 &cdev->lineinfo_changed_nb);
+	scoped_guard(write_lock_irqsave, &gdev->line_state_lock)
+		raw_notifier_chain_unregister(&gdev->line_state_notifier,
+					      &cdev->lineinfo_changed_nb);
 	bitmap_free(cdev->watched_lines);
 	gpio_device_put(gdev);
 	kfree(cdev);

drivers/gpio/gpiolib.c

@@ -1025,7 +1025,8 @@ int gpiochip_add_data_with_key(struct gpio_chip *gc, void *data,
 		}
 	}
 
-	ATOMIC_INIT_NOTIFIER_HEAD(&gdev->line_state_notifier);
+	rwlock_init(&gdev->line_state_lock);
+	RAW_INIT_NOTIFIER_HEAD(&gdev->line_state_notifier);
 	BLOCKING_INIT_NOTIFIER_HEAD(&gdev->device_notifier);
 
 	ret = init_srcu_struct(&gdev->srcu);
@@ -1056,24 +1057,19 @@ int gpiochip_add_data_with_key(struct gpio_chip *gc, void *data,
 
 		desc->gdev = gdev;
 
-		if (gc->get_direction && gpiochip_line_is_valid(gc, desc_index)) {
-			ret = gc->get_direction(gc, desc_index);
-			if (ret < 0)
-				/*
-				 * FIXME: Bail-out here once all GPIO drivers
-				 * are updated to not return errors in
-				 * situations that can be considered normal
-				 * operation.
-				 */
-				dev_warn(&gdev->dev,
-					 "%s: get_direction failed: %d\n",
-					 __func__, ret);
-
-			assign_bit(FLAG_IS_OUT, &desc->flags, !ret);
-		} else {
+		/*
+		 * We would typically want to check the return value of
+		 * get_direction() here but we must not check the return value
+		 * and bail-out as pin controllers can have pins configured to
+		 * alternate functions and return -EINVAL. Also: there's no
+		 * need to take the SRCU lock here.
+		 */
+		if (gc->get_direction && gpiochip_line_is_valid(gc, desc_index))
+			assign_bit(FLAG_IS_OUT, &desc->flags,
+				   !gc->get_direction(gc, desc_index));
+		else
 			assign_bit(FLAG_IS_OUT,
 				   &desc->flags, !gc->direction_input);
-		}
 	}
 
 	ret = of_gpiochip_add(gc);
@@ -4193,8 +4189,9 @@ EXPORT_SYMBOL_GPL(gpiod_set_array_value_cansleep);
 
 void gpiod_line_state_notify(struct gpio_desc *desc, unsigned long action)
 {
-	atomic_notifier_call_chain(&desc->gdev->line_state_notifier,
-				   action, desc);
+	guard(read_lock_irqsave)(&desc->gdev->line_state_lock);
+
+	raw_notifier_call_chain(&desc->gdev->line_state_notifier, action, desc);
 }
 
 /**

drivers/gpio/gpiolib.h

@@ -16,6 +16,7 @@
 #include <linux/gpio/driver.h>
 #include <linux/module.h>
 #include <linux/notifier.h>
+#include <linux/spinlock.h>
 #include <linux/srcu.h>
 #include <linux/workqueue.h>
 
@@ -45,6 +46,7 @@
  * @list: links gpio_device:s together for traversal
  * @line_state_notifier: used to notify subscribers about lines being
  *                       requested, released or reconfigured
+ * @line_state_lock: RW-spinlock protecting the line state notifier
  * @line_state_wq: used to emit line state events from a separate thread in
  *                 process context
  * @device_notifier: used to notify character device wait queues about the GPIO
@@ -72,7 +74,8 @@ struct gpio_device {
 	const char		*label;
 	void			*data;
 	struct list_head        list;
-	struct atomic_notifier_head line_state_notifier;
+	struct raw_notifier_head line_state_notifier;
+	rwlock_t		line_state_lock;
 	struct workqueue_struct	*line_state_wq;
 	struct blocking_notifier_head device_notifier;
 	struct srcu_struct	srcu;